1. Field of the Invention
The present invention relates to a message processing system and method for notifying a portable wireless device of incoming data messages. More particularly, the present invention relates to a system and method by which the chances of a portable wireless device receiving a data message are improved.
2. Description of the Background Art
Many portable wireless devices receive data messages from a central service facility. For example, a paging service facility transmits a phone number page, or a text message page, to a wireless pager. Many cellular service facilities offer pager-like services for cellular phones, wherein the cellular phone can receive a phone number page, a text message page, or a voice page.
Another example of a data message receiving system in the cellular phone environment concerns a voice mail service. When a caller attempts to call a cellular phone, and that phone is out of range, unpowered (either turned off or has a dead battery), or the user fails to answer the phone's rings, a central service facility will direct the caller into a voice mailbox. Later, the central service facility will transmit a "message waiting" type data message to the phone. A display on the phone will indicate to the phone's user that voice mail is waiting in the voice mailbox and perhaps other data such as the date and time of the voice mail, length of the message, whether the voice mail is urgent or normal, the caller ID data, etc.
Another example of a data message receiving system involves personal digital assistants. These devices are small computers which offer a variety of features including schedule planning, data processing, and wireless communication functions in a portable unit. Often, these personal assistants receive data messages, such as phone number pages, text pages, voice mail "message waiting" indications, "e-mail waiting" notifications, stock market updates, etc.
The message notification systems described above can be divided into one of two classes, namely a one-way message notification system or a two-way message notification system. In a one-way message notification system, the data message is transmitted from the central service facility and not acknowledged by the wireless device. In other words, the service facility has no way of knowing whether or not the wireless device received the data message. In a one-way notification system, the service facility typically repeats the data message a number of times to increase the likelihood that the wireless device received the data message. In a two-way message notification system, the wireless device transmits an acknowledgement signal back to the service facility once the data message is received. The service facility then ceases to retransmit the data message.
Both systems suffer drawbacks. In the one-way system, the service facility establishes a limit on the number of times a data message will be retransmitted. After the limited number of retransmissions, the data message is stored in a buffer allocated to the user at the service facility. If the wireless device had failed to receive the data message during the limited number of retransmissions, the user can only learn of the data message's existence and content by periodically contacting the service facility and checking for missed data messages.
Eventually, the service facility will erase a user's data messages after an extended period of time, or allow the overwriting of older data messages in a user's allocated buffer as newer messages are stored therein. Thus, it is possible for an unreviewed data message to be completely lost when a user fails to check for missed, data messages over an extended period of time, such as during a vacation.
In the two-way system, if a wireless device does not acknowledge receipt of a data message, the service facility will wait a predetermined time, for instance one-half hour, and retransmit the data message. This retransmission procedure may occur several times. If no acknowledgement signal is forthcoming from the wireless device after several retransmissions, such as three to four, the service facility will store the data message in a buffer allocated to the user. Later, if the wireless device reestablishes contact with the service facility, such as by entering a zone of coverage, the service facility will check the buffer for data messages and, if any are present, will transmit these data messages to the wireless device.
Again, the two-way system suffers drawbacks associated with the buffering system. The service facility typically limits the buffer size per user. For example, some networks limit storage to three packets of data per user (with 512 bytes of data equaling one packet). If a user's wireless device is out of range, or unpowered, for an extended period of time and that user happens to receive many packets of data, the older packets of data will be overwritten in the buffer and lost.
Another problem with the two-way system occurs when the wireless device receives the data message but its acknowledgement signal is too weak to reach the service facility. In this instance, the service facility will retransmit the data message the maximum number of times before storing the data message in the service facility's buffer. Here, however, the wireless device has received each of the retransmissions. If the user is not alert to the situation, and the user is not deleting the duplicative data messages, each retransmission will be stored in the wireless device's memory. These duplicative data messages may overwrite older data messages. Sometimes the user has not yet reviewed the older data messages, or perhaps the user was retaining the older data messages for later referral.
One attempt, in the background art, to rectify these drawbacks has been proposed by Motorola, Inc. Motorola, Inc. offers a two-way cellular phone with a built in one-way pager. If the phone is off, the pager remains on and is intended to receive any data messages. Later, when the phone is turned on, the pager will communicate the received data messages to the phone. This solution also suffers the drawbacks associated with the one-way wireless devices discussed above. Namely, if the battery power of the phone-pager combination is depleted, the pager will be unable to receive any of the data messages. Further, if the phone-pager combination is out of range, the pager will simply not receive the data messages. Either event can lead to an overrun of data messages in the central facility's buffer and a loss of important data messages.
Therefore, there exists a need in the art for a message notification system which improves the chances of a portable wireless device gaining notification of a data message. Further, there exists a need in the art for a message notification system, which eases the processing overhead on the central service facility in retransmitting data messages.